Rolling-diaphragm pump



JAMES M 5M/ 77% J. v. SMITH ROLLING-DIAPHRAGM PUMP /0r Ma Filed May 18, 1966 April 2, 1968 FIG. 1.

FIG. 2.

United States Patent 3,375,759 ROLLING-DIAPHRAGM PUMP James V. Smith, Ames, Iowa, assignor t0 Bourns, Inc. Filed May 18, 1966, Ser. No. 550,997 4 Claims. (Cl. 92-98) ABSTRACT OF THE DISCLOSURE A pump of the reciprocating-piston rolling-diaphragm type, especially adapted to pump breathing gases at very low pressures over extended periods comprising millions of cycles of operation without shedding of diaphragm material and without failure or creasing of the diaphragm. The pump comprises a resilient diaphragm and a cylinder and a piston each having an active surface to and from which the diaphragm rolls in eversive movements incident to reciprocation of the piston in the cylinder, the active surfaces being in both instances of circular cross-section and being throughout their entire extents of non-linearly varying diameter, whereby despite continuous pumping against very low pressures through millions of cycles the diaphragm does not have tendency to creasing and does not abrade or shed undesirable particles into the gases being pumped.

The invention herein disclosed pertains to recirprocatory pumps used for pumping fluids, and more particularly to improvements in that class of such pumps employing a flexible rolling diaphragm between the piston and cylinder. The present invention relates more particularly to improvements in the relative shapes of the piston and cylinder whereby extremely long life and extreme freedom from contamination of the fluid being pumped are concurrently attained.

Pumps of the general type to which the present invention directs improvements are illustrated in the patent to Otto, 2,846,983, and in British Patent 924,551. Such pumps, when used, for example, for pumping air or oxygen-enriched air in medical apparatus such as breathingaugmenter means for augmenting the breathing process in new-born infants sufiering from respiratory distress syndrome termed the hyaline membrane syndrome, for example, are often found to become defective and fail after operating a few thousands to a few hundred thousands of cycles, or earlier, and to wear, scuff, or abrade during that period to such an extent as to scrub off or shed particles of the diaphragm into the pumped fluid. In the noted example, such pollution of the fluid is extremely undesirable if not absolutely to be barred. Further, as is thought to be evident, time is not available for replacement of a defective diaphragm during use of the apparatus.

By the present invention, a relationship between the diaphragm, the piston and the cylinder of the pump is attained, such that several millions of cycles, or more, of faultless operation of the pump in all instances are easily possible, whereby when once set into operation in a critical application or case, no fear of failure or defective operation, nor of pollution of the pumped fluid, need be had. Briefly, the invention accomplishes the noted improvement by providing specially contoured surfaces on both the piston and the cylinder, between which surfaces the everting diaphragm is adapted to roll or be wrapped on and unwrapped from during the pumping action. Heretofore, principally such pumps were formed either with regular uniform cylindrical pistons and plungers, or such 3,375,759 Patented Apr. 2, 1968 I elements were made with somewhat tapered conical surfaces. In British Patent 924,551 a contoured piston operating in a regular uniform cylinder is depicted. In all such forms or configurations of everting-diaphragm pumps, the noted excessive wear and shedding of particles of diaphragm are discernible after quite short periods of low-. pressure operation. The basic causes of the noted undesirable characteristic of such everting or rolling-diaphragm pumps is apparently abrasive rubbing of one element against another during normal operation and/or the as-. sumption by the diaphragm of other than circular crosssectional shapes during everting movement to and from the piston. For example, the diaphragm has been often noted to assume a polygonal sectional configuration during pump operation, a crease being formed at each angle of the polygon. It has been found that by making the piston and the cylinder of cross-sections varying nonlinearly lengthwise, such abrasion and assumption of noncircular cross-section during eversion of the diaphragm are entirely avoided, whereby the useful life and general utility of the diaphragm are enormously increased.

When it is noted that in an exemplary case of hyaline membrane syndrome an infant may have an average respiration rate of the order of more than one hundred cycles per minute, and that often the syndrome exists for a week or more, it becomes apparent that faultless operation of the diaphragm without detectable shedding of particles throughout a minimum of two million cycles is desired as absolute minimal guaranteed operability. Pumps according to the invention, utilizing regularly made commercially-available conical diaphragms, are found to anticipate such operability criterion or requirement.

The preceding brief general description of the background and means of the invention make it apparent that it is a prinicpal object of the invention to provide novel useful and unobvious general improvements in rolling diaphragm pumps. Other and more specific objects, and advantages of the invention, will hereinafter be set out or made apparent in the appended claims and following description of a preferred exemplary embodiment of a rolling-diaphragm pump according to the invention, reference being made in the description to the appended drawings forming a part of this specification. In the drawings:

FIGURE 1 is a longitudinal sectional View of the principal and essential components of the previously mentioned exemplary rolling-diaphragm pump, depicting the piston in fully withdrawn or rearward position;

FIGURE 2 is a view similar to FIGURE 1, but with portions broken away, depicting the piston in fully entered or forward position, and the diaphragm everted from its previous position;

FIGURE 3 is a diagram illustrating configuration data relative to the cylinder of the pump shown in FIGURE 1; and

FIGURE 4 is a diagram illustrating configuration data relative to the piston of the pump shown in FIGURE 1.

Referring to the drawings, it is to be understood that the depicted structure is exemplary only, that the invention does require a cylinder in the sense of a cavity having an inner wall portion of substantially circular cross-section, a piston or elongate plunger reciprocable in the cavity or cylinder, the plunger likewise having a portion of substantially circular cross-section, and a tubula-r diaphragm One open end portion of which is peripherally sealed to and held by the cylinder and an opposite open end portion of which is sealed to and held by the piston or plunger. Those three essentials are, in general, components of all rolling-diaphragm pumps. In the case of the present invention, however, and contra to the prior art, the outside diameter of the piston, and the inside diameter of the cylinder as well, vary nonuniformly along the active portion of the length of the respective component. By active portion is meant that portion of the surface of the respective component with which the diaphragm comes into contact. The nonlinear variation of diameter of both piston and cylinder is such that in rolling off from the contoured surface of the piston onto the complementary contoured inner surface of the cylinder, and vice versa, as the piston reciprocates to and fro between extremes of its travel, the diaphragm does not rub against either a portion of itself nor against any portion of either the piston or the cylinder, and further does not crease or otherwise depart from a substantially circular cross-section at any station along its length, irrespective of how low the positive pressure differential acting on the pumping face of the piston and diaphragm is. While in the exemplary illustrated arrangement according to the invention the diaphragm is of slightly conical configuration, it will hereinafter be made evident that complementary configurations of piston and cylinders of nonuniformly varying diameters can be formed and provided to accommodate uniformly cylindrical diaphragms.

In FIGURES l and 2 the pump is shown to comprise a chamber or recess forming cylinder 10, a piston 12, and a rolling diaphragm 14. The cylinder is preferably made in two sections, 10a and 10b, each having an outer peripheral flange complementary to that of the other whereby the sections may be detachably secured each to the other as by means of bolts 10d, 10f. Section 10b is provided with an annular recess 10r formed in the end face of the section abutting the complementary end face of section 10a, the recess being dimensioned and arranged .to tightly receive therein the annular enlarged end or bead 140 of the diaphragm 14. Diaphragm 14, as used in the illustrated structure, may be identical with a commercially-available diaphragm marketed by Bellofram Corp., 36 Blanchard Road, Burlington, Massachusetts, as part No. 3-175-175 CB'B. The diaphragm is cupshaped with a flat circular bottom 14b and a conical rolling wall portion 14w terminated by bead 140. The bottom of the cup is pierced or apertured for passage of the rod 121' of the piston, and is retained or clamped between the end wall and the retainer member 14a of the piston proper, whereby only the conical intermediate or wall portion of the diaphragm flexes and rolls during pump operation. The piston is preferably constructed as depicted, but other equivalent arrangements of parts may be used.

Thus the beaded end of the diaphragm is arranged to be gripped and held between sections 10a and 10b of cylinder 10; and at that annular juncture sealant may be employed if desired. The piston is of somewhat smaller maximum outside diameter than the minimum inside diameter of the cylinder, as indicated in FIGURES 1 and 2, whereby there is space therebetween in which portions of the wall of the cup-like diaphragm may roll onto and off of the outer active surface of the piston and the inner active wall surface of the cylinder. In operation the piston reciprocates within a variable stroke range demarked by an extreme outward position relative to the cylinder as indicated in FIGURE 1, and an extreme inward position as indicated in FIGURE 2, being reciprocated by means which are or may be conventional and which per se are not of this invention. Fluid to be pumped is admitted to the interior of cylinder 10 via an orifice or connection such as 10c, or a mate (not shown) to that connection, it being understood that in practice the pressure in the closed chamber 102 in the cylinder is substantially always higher than that of the ambient fluid or atmosphere, the fluid to be pumped (usually a controlled mixture of gases) being supplied to the cylinder from a source and pumped by the piston and diaphragm through an orifice or connection 100 to valve and conduit means to where the fluid is utilized. For example, in the previously mentioned breathing augmenting apparatus for infants, in which the present invention has found use, moist, oxygen-enriched air is supplied via an intake valve and orifice connection to chamber 102 during the outward stroke of the piston, and is discharged via an outlet connection and valve to .a nasal mask sealed to the nasal area of the infant. The inlet and outlet to the cylinder may be the same, or different, depending upon the type of valve employed at the cylinder head. The stroke of the piston and speed of reciprocation are both closely adjustable over wide ranges within the noted extreme range, whereby respiration volume and rate are controllable. The pressure of the pumped gases in the cited example is low, being of the order of from 2 cm. to a maximum of cm. water pressure, which may accentuate any tendency for the diaphragm to assume a noncircular (polygonal) configuration and to scuff or abrade and shed particles.

It has been found that the rolling diaphragm may be induced to refrain from assuming a polygonal or noncircul-ar section during rolling onto either of the piston and cylinder from the other thereof, by making the profiles nonuniform, that is, the diameters of the active surfaces of these latter components such that they vary nonlinearly, along at least the active portions of the respective surfaces upon which the diaphragm is rolled during pumping. Thus, as indicated in FIGURES 1 and 2, the surface profiles of the diaphragm-contacting portions of the surfaces of the piston and cylinder are such as to conform to the surface or shape the diaphragm assumes when it is rolled back and forth in a free condition with no fluid pressure acting on it. Thus, commencing at the head end of the piston and progressing toward the skirt or outward end, the outside diameter gradually decreases along a major portion of the active or diaphragm-contacting surface, then becomes substantially uniform at a minimum diameter, and then increases. Thus there is a reversal of curvature in the longitudinal outline of the active surface of the piston. Similarly, in the case of the interior or active surface of the cylinder, commencing at the outer or open end, the inside diameter gradually increases over a major portion of the active-surface length r to a maximum, and then decreases until the curved lip 10: (FIGURE 1) adjacent the bead of the diaphragm is reached.

Exemplary diametral dimensions of the active surface of the piston and the cylinder are tabulated hereinafter in Table I, the dimensions being taken at stations A, B, C, D, E, F, G, H, and I (FIGURE 4) along the piston, and at similar stations A, B, C, D, E, F, G, H, and I along the interior of the cylinder (FIGURE 3); the exemplary dimensions being for a piston-and-cylinder combination of sizes of the order indicated, namely, for a 1% inch piston (nominal) and 1% inch cylinder. The exact profiles for the active surfaces of the piston and cylinder, for any particular maximum stroke and diameter, are easily obtained by securing the ends of the otherwise free diaphragm and moving the piston end through the specified stroke, recording the profile of the rolling portion of the diaphragm at a series of stations during the stroke, and deriving the required profiles by producing respective envelope curves corresponding to the points at which the rolling portion of the diaphragm becomes stationary, and producing respective surfaces of revolution from the envelope curves. Since the profiles of the piston and cylinder thus determined correspond exactly to the surface configurations that the diaphragm would naturally assume due to its inherent resilience, the diaphragm will conform to the thus produced surfaces without creasing or scrubbing. Piston, cylinder and diaphragm combinations thus produced have been found to operate entirely satisfactorily through tens of millions of cycles, without detectable contamination of the pumped fluid.

Stations spaced inch apart.

The preceding detailed description of-a specific exemplary embodiment of the invention, including specific d1- mensional data, together with a detailed explanation of the mode of deriving dimensional data for piston and cylinder configurations for any other size of rolling diaphragm pump, make it evident that the aforestated objects of the invention have been fully achieved. Also made evident is the fact that changes within the true spirit and scope of the invention will occur to those skilled in the art upon consideration of this disclosure. Accordingly, it is not desired to restrict the scope of the claimed invention to exact shapes, sizes and interrelationships of the components of the exemplary structure shown and described, except as may be required by the appended claims.

I claim:

1. A rolling-diaphragm pump comprising:

first means, including means providing a cylinder having a substantially closed end forming with an inner wall surface thereof of a piston-receiving space, said inner wall having an elongate active surface portion of circular cross-section the entire extent of which active surface portion is of nonlinearly varying diameter;

second means, including a piston having a head and means for reciprocating the piston head to and fro in said space to alternately increase and decrease the occupied volume in said space, said piston head having an elongate active surface portion of circular cross-section the entire extent of which active surface portion is of nonlinearly varying diameter, and said piston head being dimensioned to provide an annular space therearound and encircled by said inner wall of said cylinder; and

third means, including an elongate resilient rolling diaphragm terminated by first and second end portions separated by an intermediate tubular body portion having first and second elongate wall surfaces, said first end portion being secured to said first means along an annular zone around the latter whereby to remain sealed and stationary relative thereto and said second end portion being secured to said piston along an annular zone around the latter whereby to reciprocate therewith relative to said first means and whereby gas in said space is prevented from escaping from said space past said end portions of said diaphragm, said active surface portions of said cylinder and said piston being spaced apart and of complementary configuration such that during reciprocation of said piston head portions of said first elongate wall surface of said sleeve roll and evert freely without creasing to and from said active portion of said inner wall surface of said cylinder from and to said active surface portion of said elongate surface of said piston head whereby during long-continued operation of said pump and repetitive eversion of said diaphragm the latter does not crease and does not shed gas-contaminating particles. 2. A rolling-diaphragm pump according to claim 1, in which said first end of said diaphragm comprises an annular ring bead and in which said first means forms an annular recess tightly receiving said head whereby to concurrently effect the securement of said first end portion of said diaphragm to said first means at said annular zone and to effect thereat an annular fluid-tight seal.

3. A rolling-diaphragm pump according to claim 1, in which said inner wall surface of said cylinder and said elongate surface of said piston are of nonlinearly varying diametrical dimension as stated and are of such surficial configuration that in rolling to and from said surfaces said diaphragm follows substantially exactly the course it would follow if no differential gas pressure were exerted thereon and said active surface portions were absent.

4. A rolling-diaphragm pump comprising: first means, including cylinder means providing a pistonreceiving space encircled by an inner wall having an active surface disposed to receive a rolling diaphragm and the entire extent of which active surface is of circular cross-section of nonlinearly varying diameter formed by the cylinder means; second means, including piston means having a piston head arranged for reciprocatory movement to and fro in said space, said piston means having an elongate active surface disposed to receive a rolling diaphragm and the entire extent of which active surface is of circular cross-section of nonlinearly varying diameter and said piston head being dimensioned to provide a generally annular space around said piston between the piston head and the adjacent encircling inner wall of said cylinder means, said active surfaces being contoured to substantially conform to respective configurations of the respectively received surfaces of a resilient rolling diaphragm assumed by the latter when freely inverting; and

third means, including a flexible resilient rolling-diaphragm having a generally tubular body portion comprising an everting portion having surfaces arranged to be received on the active surfaces of said piston means and said cylinder means, said diaphragm being terminated at the ends thereof by respective first and second end portions;

said first means having provision for securing the first end portion of said diaphragm peripherally thereto at a station along said inner wall, and said second means having provision for securing the second end portion of said diaphragm at the periphery thereof to said piston head, whereby upon relative reciprocation of said piston means and said cylinder means a portion of said diaphragm between said end portions rolls off to one and onto the other of said piston head and said inner wall of said cylinder means in said annular space, thus alternately uncovering and covering respective active surfaces of each thereof;

said piston head and said inner wall having nonlinearly varying diametral dimensions over a length thereof contacted and uncovered by said diaphragm, the diametral dimensions varying so as to provide surface contours substantially matching the surface configuration assumed by the diaphragm when said second end portion is reciprocated with the said body portion free from effects of applied pressure.

(References on following page) 7 8 References Cited FOREIGN PATENTS UNITED STATES PATENTS 1,053,207 9/1953 France. 2,721,579 10/1955 Sexton 92 100 1,330,164 5/1963 France- 2,950,739 8/1960 Lofink 92-98 5 14,235 7/1880 Germany- 3,118,389 1/1964 Camp 103-150 3,158,152 11/1964 Bloom 230 17O ROBERT M. WALKER, Pllmal'y Examiner.

3,185,041 5/1965 Stein 92-98 WILLIAM L. FREEH, Examiner. 

